Process of sintering and apparatus therefor



March 31. 1925. 1,531,695

F: A. EUSTIS P y A PROCESS OF SNTEHING AND APPARATUS THEREFOR FiledNOV. 9, 1920 I 7 y 7 1L ,l0 5 Iv/12 1 ',/f 9 a/z 3 10 5i 3 4 'L 'l- 'l I :I ::Z'I- -II'IILIIBI :52211112222211211122 `1:I: f i 1 1 I Patented. Mar. 31, 1925.

PATENT i OFFICE.

.FREDERIC n EUSTIs, oF MILTON, MASSACHUSETTS..

PROCESS F SINTERING AND .AEIA.RA'.I."U'S THEREFOR.

lApplication led November 9, 19202 Serial No. 422,792.

T0 all whom it may concern.'

Be it known that I, FREDERIC A. EUSTIS, a citizen of the United States of America, and resident of Milton. in the county of Norfolk and State of Massachusetts, have invented new and. useful Improvements in Processes of Sintering Therefor, of which the following is a specification. I

This invention relates to a process of sintering fine ores or'other fine materials, and to apparatus therefor. Sintering, generally speaking, consists in subjecting the fine ore or other material, mixed with a suitablel proportion of fine fuel, to a burning or roasting treatment, by which the small particles are fused and agglomerated into a solidified, porous mass. The processv is usually performed in a sintering pan in which a bed or'charge of the material is supported on a suitable grate while the combustion of the fuel mixed with the material takes place, aided by a draft of air.

The object of the present invention is to increase the efficiency of sintering as heretofore practiced, toeffect economies of fuel and time, and `otherwise to improve and simplify the process. of sintering and apparatus therefor, as hereinafter more fullyY described.

The process, stated in brief general terms, consists in passing air through a charge which has just been sintered, into a fresh charge to be sintered, ,whereby the air is heated by the first charge and the latter' isnace containing the fresh charge, and causf ing the air to pass through the first sintering furnace and the hot charge .therein and thence into the second furnace. When the charge. in the second furnace has been completely burned, or substantially so, its outg let flue is in turn connected to the inlet flue of a third furnace containing :mother fresh charge, and so on. The cool air pass-V ing through each furnace and charge preand Apparatus viously sintered is not only heated so as to"y deliver la hot blast of air into the next succeeding fresh charge, butalso cools the already sintere'd charge and makes it possible to dump it or otherwise handle it without damage to apparatus or danger to the operat1ves,

The process will now be described more l Ain 4detail in connection with apparatus for performing it.

In the accompanying drawingswhich illustrate apparatus in somewhat diagrammatic form, suitable for practicing the Figure l is a side elevation' of two sintering furnaces connected in series; and

Figure 2 is an enlarged section on line 2 2 of Fig. 1.

As illustrated in the drawings, the furnaces are mounted on cars or wheel trucks, preferably running on rails, so that furnaces containing finished charges may readily be disconnected and removed, and fresh ones added, as the process progresses.

Each furnace comprises a pan 3, in which afsuitable grate 4 is supported above the bottom, leaving a space or empty chamber 5, which may be provided with a floor 6 of suitable refractory material such as brick. C represents the charge of sinter'resting on the grate' 4.

A weighted hood 7 made with depending side and end walls 8 is lowered into the pan 3 and on top of the charge. The walls 8 are. forced down into the charge by the weight of the hood,l aided if necessary' by additional force. The penetration of the .Walls 8 into the ore may be facilitated by beveling or sharpening their'edges as shown at 9. The walls 8 will be preferably pushed down substantially to the grate 4., or'at any rate far enough to insure thepassage of the air and gases through the vcharge and the grate without escaping in undue amounts upward around the outside of the Walls 8.. The space 5 below the grate is provided with an outlet flue 10, preferably at one end vof the pan 3 for convenient connection to the inlet flue of'the next furnace.

The hood 7 Ais -provided with an air in,- take flue 11, communicating with the space erably disposed at the end of the furnace vwithin the hood above the charge, and prefvlas ranged branches 13 for delivering jets of oil or gas to the interior of the hood for the purpose ofV igniting the charge.

' In operation, air is forced by pressure 5 into the intake flue 1l, or 1s drawn 1n by suction at the 'delivery end, and passes into the top of hood 7, downward through the charge C and grate f1 into the space 5,`and thence passes out with the 'products of combustion through outlet, flue 10., The sintering action is as usual. The vweight of the hood may be made suiiicient to overbalance the air pressure, when the air is supplied under pressure, 1n whlclrcase no locking devices will be necessary.

`When the sintering is completedl or subtantially completed in one furnace, for example in furnace A (Fig. 1) the outlet flue 10 of furnace A is connected by any suitable means, such as the conduit 1.4, to the delivered hot to furnace B.

intake iiue 11 of furnace A, cools that fur-4 nace and its charge so that by the time it has. performed its function of heating the charge in furnace B the furnace A may be disconnected from furnace B and discharged without danger to apparatus or operatives from excessive heat. As soon as the charge in furnace B is burned, the outlet fiue of furnace. B may be connected 'as before to 40 the inlet flue of another furnace containing a fresh charge, and so on indefinitely, each Afinished charge furnishing the hot blast for the next succeeding fresh charge, and being cooled off in the process.

The successive treatment of two or more individual charges in series, and the utilization of the heat stored up in a previously sinteredv charge to heat the succeeding chargegin accordance with the presentinvention, possesses two major advantages.

First, it effects a substantial saving in fuel;l

and second, it makes it possible without sacrificing fuel economy to avoid excessive dryingv ofthe charge, or any part thereof.

It will be apparent, and I have demonstrated in practice, that Ithe sintering of a number of charges successively, and the heating of each successive charge by the heat stored u in^the previously sintered charge, will 'su stantially reduce the amount offuel consumedas compared with existing methods of sintering in which each charge is ignited'while cold, and the stored heat in the finished charge is wasted.

It may be suggested that the fuel -economy of the present invention might be achieved to a measurable degree, although not fully,

by sintering a very thick bed of material in a single furnace, in which case the burningat the inlet side of the bed first to be ignited, that is, the top of-the charge inthe arrangement shown in the drawings, would to some extent at least pre-heat thel material at they outlet side of the bed, that is, Athe bottom of the charge as shown in the drawings, and so effect some saving of fuel. If, however, an unduly thick charge is used excessive drying the the material occurs at the Aoutlet sideof the bed owing to the length of time during which that part of the vcharge is subjected to the drying action of the hot gases producedby combustion. Excessive drying of the charge, or any part of it, is a thing distinctly to be avoided, since drying ldestroysthe porous nature of theV charge and reduces it to powder, which packs and interferes with the draft; moreover, the fine dried material will fall through the grate. It is therefore desirable to use a comparatively thin charge of material, in which the combustion will work through thes bed, and the sintering will take place, quickly enough to avoid undue drying of any part of the charge. Moreover, even from the standpoint of fuel economy the treatment of a thick bed by present methods only partially accomplishes the result because each new charge is ignited cold, without provision for the hotblast of air which is especially advantageous at the :initial stage. It will thus be seen that with sintering YES- methods heretofore used, two objects greatly to be desired, namely maximum fuel e'iiiciency and avoidance of undue drying, appear to be irreconcilable.v If the bed of material is thick. enough to give a substantial saving of fuel'by pre-heating one side of the bed by burning which starts on the other side, excessive drying takes place.

`And' if a .comparatively thin bed of material is used in order to avoid the drying difficulty, a maximum amount of fuel is required.

These conflicting' conditions are wholly reconciled by the present invention, which makes it possible to use a comparatively thin bed or charge of material, thus com- .pletely eliminating the drying trouble, and

at'the same time to use the minimum amount of fuel byv utilizing the heat generated in a previously sintered charge to promote combustion in the next. succeeding fresh charge.

A further advantage of the present inventionl is that it tends to equalize the heat during the sintering operation, and supplies heat to thev furnace proportionally to its needs. Thus at the time of ignitionand during the initial stages of the sintering, when heat is most needed, the air blast comes hottest from the finished charge to the fresh succeeding them respectively, the sintering,V

of each charge being substantially com-Y pleted before the utilization of its heat for heating the succeeding charge.

2. A method of sintering which com'- prises successively sintering a plurality of charges of fine material, and passing the air for supporting the combustion of each successive sintering operation through a previously sintered charge\while the latter is still hot, whereby the charge to besintered will be supplied with a hot air blast, andthe charge already sintered' will be cooled. s

' rality of independent enclosed sintering' 3. Sinteringapparatus comprising a plu? furnaces adapted to be operated successively, each having a grate adapted to support the charge and an air inlet at one side of the grate and an outlet at thel other sidev of the grate, and Aa separable connection between the outlet of one and the inlet of another furnace connecting the furnaces in series, whereby the air for supporting combustion-'in the latter furnace will'bepaused to passV through the heated Y charge. of the former furnace.

4. Sintering apparatus comprisinga plurality ward through -walls of the pan.

sively, each having a grate-adapted to sup'v port the charge and an air inlet above the grate and an outlet Vbelow theh grate, and a separable .connection between the outlet of one furnace and the inlet of another furnace connecting the furnaces in series, whereby the'air for -supporting combustion in the latter furnace will be caused to pass downformer furnace. d

5. Sintering apparatus comprising avplurality of independent sinteringfurnaces adapted to be operated successively,` each having a grate adapted to 'support thel charge and an air inlet at one side of the the-heated charge of the grate and an outletat the other side of the grate, said furnaces being independently mounted on wheels and -cOnSequentIy movable relatively one, to another, and a separable connection between the .outlet "of one furnace and the inlet of another' furnace connecting. the furnaces in series, whereby the air for supporting combustion in the latter furnace will be caused topass through the heated `charge of the former furnace. A

6. A sintering furnace comprising a'pan having a grate adapted to support' a charm; of ore,and -a hood having depending wa adapted to be forced down into the charge. A

inside of the walls of the p'an.

7. A sintering furnace comprising a panv having a grate adapted to support a charge of ore, and a weighted hood having depend-.

ing walls adapted to be forced down by its own weight into the charge inside -of thel Signed by me at iiii m Y. Y Boston, Massachusetta,

thisirfth day of November, 1920. "f v of independent enclosed' -fu'rnaaces adapted tobe operated-succes 

